High pressure generating apparatus



Sept. 28, 1965 KlYOSHl INOUE HIGH PRESSURE GENERATING APPARATUS Filed April 21. 1961 FIG. 2

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IN V EN TOR.

Time United States Patent 3,208,254 HIGH PRESSURE GENERATING APPARATUS Kiyoshi Inoue, 182 3-chome, Tamagawa-Yogamachi, Setagaya-ku, Tokyo, Japan Filed Apr. 21, 1961, Ser. No. 104,758 Claims priority, application Japan, Apr. 23, 1960, 35/22,505; June 13, 1960, 35/27,871 2 Claims. (Cl. 7256) The present invention relates to devices and methods for generating high pressures.

When an electrodischarge is effected across a gap between electrodes in a liquid, a high pressure is generated in the discharge zone and propagates through said liquid in the form of an impulse Wave, producing a mechanical force. I have already proposed to utilize such a mechanical force for pressing and other machining operations as well as for a power source.

This invention contemplates generating a high pressure as referred to above but by a different construction. A further object of the invention is to increase the pressure generated by the above-mentioned technique. A still further object of the present invention is to generate a plurality of pressures having a predetermined time lag for facilitating machining operations such as pressing. Yet another object of the present invention is to provide a high pressure generating apparatus, which has a low energy loss and is easy to handle.

The present invention proposes apparatus for generat ing a high pressure in a liquid in the form of an impulse Wave, by instantaneous evaporation, fusion-cutting and the like of a wire-shaped fusible conductor arranged within said liquid as a portion of an electric circuit, by means of a heavy pulse of electric current supplied from an ap propriate AC. or D.C. source.

The liquid should be an uncompressible liquid, whether it is electrically conductive or insulating. Moreover, in the present invention, a plurality of said fusible conductors can be provided, and by passing a heavy electric current through said conductors a higher pressure can be obtained.

Further, in accordance with the present invention, said fusible conductors can be arranged in a closed receptacle filled with a liquid, and by passing an electric current through said conductors to evaporate and cut them by fusion, a fluid pressure in the form of an impulse wave as well as an expansion pressure due to the heat caused by the evaporation and cutting by fusion are added together and directed against inner walls of said receptacle, whereby both pressures are simultaneously utilized.

Moreover, according to the present invention, in such a double acting device wherein, as mentioned above, both impulse pressure and expansion pressure can be utilized simultaneously for machining a work piece, a distinct electrodischarge gap is provided by separately arranging a counterpole adjacent to said fusible conductors. Then, by an impulse electrodischarge, that is,

by a spark discharge across said gap, a directional character can be imparted to said pressures. Furthermore, in the above-mentioned construction, a work piece can be manipulated by each impulse of pressure having a time-lag due to the evaporation and fusion-cutting of said wire-formed fusible conductor as well as electrodischarge caused across said discharging gap. Still further, the apparatus according to this invention enables generating an electrodischarge between supporting pieces for said fusible conductor, after the latter has been evaporated and thereby a third impulse pressure can be obtained.

Moreover, an intermediate electrode can be. inserted in the gap formed by the fusion-cutting of said fusible conductor, and thereby a more powerful pressure can 3,208,254 Patented Sept. 28, 1965 be obtained due to an electrodischarge effected by said intermediate electrode.

According to the present invention, the apparatus can be provided with a series-connected resonance circuit which is in parallel with the fusible conductor. By dividing the wave form of discharge current at the time of discharging across the gap after the evaporation a higher liquid pressure in the form of an impulse Wave can be produced continuously for a limited period of time.

The present invention will be made clear by reference to the accompanying drawings illustrating typical embodiments of this invention and in which:

FIG. 1 is a diagrammatic view of an apparatus according to the present invention for generating a high fluid pressure in the form of an impulse Wave.

FIG. 2 is a diagrammatic view of an apparatus according to the present invention for generating a high fluid pressure used for press machining, wherein a distinct electrodischarge gap defined by opposite electrodes is provided.

FIG. 3 illustrates a variation of the apparatus of FIG. 2, wherein is provided an intermediate electrode to form an electrodischarge gap.

FIG. 4 shows a time-transition characteristic of the pressures generated respectively by the evaporation and fusion-cutting of the fusible conductor due to electric current being passed therethrough and the distinct electrodischarge gap arranged adjacent to said fusible conductor.

Referring to FIG. 1, 1 is a wire-shaped fusible conductor; 3 is a container for a liquid 2 such as a mobile oil; 5 is an electrode supporting said conductor 1; 4 is an apparatus for generating a pulse of electric current; and 6 is a switch for controlling the electric current.

When the switch 6 is closed, a pulse of heavy current passes from a condenser 9, which has been charged by a D.C. source 8, through the fusible conductor 1 constituting a discharge circuit for said condenser. Said conductor 1 is instantaneously evaporated and cut by fusion, and a .high fluid pressure in the form of pulse wave propagates through said liquid, together with an expansion pressure in the fluid are simultaneously generated.

It is not sufliciently clear on what theoretical mechanism the generation of such a fluid pressure is based. The mechanism may be considered to be as follows: if, in either an electrically insulating or conductive liquid, a fusible conductor is inserted as a part of an electric circuit extending from a pulse current source, and a current heavy enough to evaporate said conductor instantaneously is passed therethrough whereby the conductor reaches red-heat, the conductor can be caused to pass through its fusion and boiling points up to a higher temperature (which is estimated to be over several tens of thousands of degrees). Such a phenomenon will take place in a very short period of time such as, for example, in the order of less than a fraction of a millisecond, provided that the electric power is sufliciently high and the pulse of current is high. In this case, the vaporized conductor not only expands, but also the liquid surrounding said conductor gasifies instantaneously due to said high temperature. The volumetric expansion of the liquid around the center of the conductor occurs instantaneously or explosively. A liquid pressure of pulse wave form is produced by such an instantaneous action. The resulting pressure can be utilized as a power source for press work and other workings, and the pressure can effectively be applied to workpieces to be machined.

The time which is required for vaporization as well as the fusion-cutting of the fusible conductor is dependent substantially on the instantaneous character of the supply of electric power. The condition of the generation of pressure and its action will be aifected thereby. Nevertheless, it is possible to use an ordinary AC. or DC. source, provided that some safety means is provided.

FIG. 2 illustrates an embodiment of the present invention, wherein the pressure generating apparatus is utilized for working a press and wherein a discharge gap G defined by spaced discharge electrodes is provided adjacent the fusible conductor 1. The discharge electrodes are used for several purposes as noted above.

In FIG. 2, 10 is a piece to be machined; 11 is a closa-ble receptacle filled with liquid 2 and supporting the piece to, be machined 10; is an electrode supporting a wireshaped fusible conductor 1; 12 is a hole to exhaust the air etc. from mould 15, when the work piece is machined to the shape of the mould by the liquid pressure in the form, of pulses generated inside the apparatus; 7 is a resonant circuit connected in parallel with the fusible conductor 1 with respect to pulse current generating means 4; 6 and 13 are switches for supplying a potential or electric current pulse respectively from condensers 9 and 14 to the fusible conductor 1 and the electrodischarge gap G.

A plurality of said fusible conductors can be arranged in parallel (not illustrated). If, through each conductor is passed a pulse of electric current, each conductor is simultaneously evaporated and cut by fusion. The liquid pressure generated in the form of a pulse wave and the expansion pressure due to volumetric expansion of the liquid can be summed up to a higher pressure, which acts against the inner wall of closed container 11, and also acts against the work piece 10 which is to be machined to perform press, bending and other machining operations relative to the shape of the mould 15.

Further if by closing the switch 13, an electrodischarge is effected across the discharge gap G substantially synchronously with the evaporation and fusion-cutting by the passage of current through the fusible conductor 1, the pressure of pulse wave form generated by the evaporation and fusion-cutting of the conductor 1 is given a downward propagatingdirectional character, under the effect of the pressure resulting from the discharge across the gap G. As a result, the effective pressure is increased.

The machining of work pieces can be performed either by causing said both pulse-form pressures to act integrally or by causing a time lag between said both pressures as illustrated in FIG. 4.

The pressure generating means, utilizing the phenomenon of evaporating and fusion-cutting of a fusible conductor, requires a renewal of the fusible conductor for each stage of pressure generation and, in fact, this is a troublesome matter. In order to avoid said disadvantage, when a further pressure is necessary after the evaporation followed by the fusion-cutting of the conductor, or when a sufficient pressure is not obtained by the previous evaporation followed by fusion-cutting of the conductor, an electrodischarge is effected across the gap between the electrodes which supported the now fused conductor without renewal of the conductor in order to produce an additional discharge pressure in the form of a pulse wave.

By the above step the operation can be simplified and any desirable high pressure can be obtained. However, when once the fusion-cutting has been effected, the resulting gap becomes enlarged and a larger voltage must be impressed to effect an electric discharge across said gap. Accordingly, in such a case, in the apparatus according to this invention, an electrodischarge is effected across the gap G by closing the switch 13, after the fusible conductor 1 has been fusion-cut and evaporated by the electric current passed through said conductor. The electrodes 5 which supported the now open fusible conductor are affected by this discharge across the gap G, and the starting voltage required for an electrodischarge between said electrodes 5 becomes lower and a dishcharge between Thus, in this case, the discharge gap G can be used for starting an electrodischarge between said electrodes 5.

By this method, the reduction of energy loss can be rea-' lized. Additionally as the pressure generated due to said electrodischarge, after the evaporation accompanied by the fusion-cutting, is proportional to the amount of consumption of the wire-formed fusible conductor, the pressure in this case can be increased as compared with the simple method of generating pressure by an electrodischarge across the gap of the electrodes. Moreover, the supporting electrodes 5 may be so arranged as to be fed, after the evaporation and fusion-cutting of the conductor 1 by the passing of current through said conductor, by the feeding of said electrodes 5 to narrow the gap. Discharge by a condenser can be made possible and the electrodischarge pressure in the form of pulse can also be applied by integration.

A series resonance circuit 7 can be connected in parallel with the conductor 1, and if said circuit is brought into resonance at the time of the electrodischarge across the gap after the evaporation followed by fusion-cutting of said wire-formed fusible conductor, the wave form of the discharge current by the condenser is divided by its resonance current and said discharge current begins to circulate in the form of numerous pulse-currents and the thusly-generated pressure is doubled as has been experimentally confirmed.

The circuit illustrated in FIG. 3 also shows an effective means, according to this invention, to increase the pulse pressure generated by the electrodischarge across a gap between the electrodes 5 which support the previously opened fusible conductor after the evaporation and fusion-cutting of said fusible conductor. 16 is an intermediate electrode which is to be inserted by a driving motor 17 between the gap formed by the evaporation followed by fusion-cutting of the conductor 1 by passing current therethrough. The intervention of said intermediate electrode 16 provides two discharge gaps, one being situated between one supporting electrode of the fusible conductor and the intermediate electrode, while the other being between the other supporting electrode of the fusible conductor and the intermediate conductor. Said two gaps are available for discharge and the discharge pressures in the form of pulse waves generated in each electrodischarge can be integrated. As a result, the generated pressure can be doubled.

In press machining or the like, frequently it is impossible to add pressure applied to a work piece at one time because of its shape or the constituting material itself, and it is required to add discrete pressures on a work piece consecutively at intervals. In such a case, it is advisable to arrange a plurality of fusible conductors in parallel, as explained above, and to give necessary time lags between each evaporation and fusion-cutting of said fusible conductors by varying their respective materials and sizes or their respective voltage applying time. On the other hand, when respective electric current or voltage pulses are applied simultaneously to the fusible conductors 1 and across the discharge gaps G for generating their respective discharge pressure, the pressure A due to electrodischarge across the gap G reaches its peak earlier than the pressure B due to evaporation and fusion-cutting of the conductor 1, as illustrated in FIG. 4. By utilizing this time lag between the peaks appearing respectively in the pressures A and B, the same result as referred to above can be obtained.

As described in the various foregoing examples, the high pressure generating apparatus and technique of this invention is adapted to generate a high pressure without loss of energy and with a simple handling, and also possesses characteristics enabling complex machining in presses and the like.

In the following, experimentally measured results of a liquid pressure in the form of a pulse wave generated in liquid by evaporation and fusion cutting of a fusible conductor due to passing current therethrough will be given by way of exampe.

A copper wire of 1 mm. diameter was stretched as a fusible conductor between its supporting electrodes so as to secure its effective stretch length of 35 mm. within a closed container of a capacity of 1 litre filled with water. Further, a condenser of a capacity of 1,000 ,uf. was charged to 3 kv. (the charge energy is 4.5 K joules). By applying this electric charge to the discharge circuit of said copper wire through a spark gap, a pulse current was circulated in said discharge circuit. The maximum value of this pulse current was about 40 kva., and said copper wire was cut by fusion after approximately 200a seconds, and as a result, a liquid pressure in the form of a pulse Wave acted against the inner wall of said closed container. The magnitude of the pressure was assumed approximately 2.5 tons/cm. at the maximum. Such a measurement of the pressure was carried out as follows:

Many circular holes of diiferent diameters were made in a part of said closed container, and a metallic sheet of known material and thickness was closely bonded to the inside wall of that part of said container. Then the magnitude of the pressure was measured from the conditions of respective permanent plastic deformations of said metallic sheet opposite said each hole after said water pressure had acted.

The present invention having been described in connection with the foregoing examples of embodiment, it is of course possible to provide various other modifications without departing from the scope or the spirit of this invention as claimed in the following claims.

What is claimed:

1. An apparatus for deforming a workpiece by the application thereto of fluid pressure, comprising:

housing means defining with the workpiece a generally closed chamber substantially filled with dielectric liquid;

a pair of spaced-apart conductors juxtaposed in said chamber and immersed in said liquid while defining between them a first electrical-discharge gap extending generally parallel to the workpiece;

means forming a second electrical-discharge gap immersed in said liquid along a side of said first gap remote from said workpiece;

a fusible member bridging said conductors and spanning said first gap; and

circuit means connected across said conductors and said means defining said second gap for:

applying to the latter a first current pulse suflicient to generate an electric discharge across said second gap and thereby produce a hydraulic-pressure pulse in said liquid,

applying a second current pulse to said conductors of an intensity sufficient to precipitously fuse said member and thereby generate a workpieceshaping hydraulic wave in said liquid prior to decay of said hydraulic-pressure pulse, and applying a third current pulse to said conductors of an intensity sufficient to generate a discharge across said first gap upon fusing of said member. 2. A method of deforming a workpiece by the application thereto of fluid pressure comprising the steps of:

passing a first current pulse across a discharge gap in a liquid to produce a hydraulic-pressure pulse therein; applying a second current pulse to a pair of spacedapart conductors disposed between said workpiece and said gap while said conductors are bridged by a fusible member adapted to be burned through by said second current pulse prior to decay of said hydraulic-pressure wave; and thereafter applying a third current pulse across said conductors to generate an electric discharge therebetween, said discharges and the fusion of said member producing a hydraulic pressure in said liquid sufficient to deform said workpiece.

References Cited by the Examiner UNITED STATES PATENTS 528,661 3/94 Engel 219149 690,856 1/02 Hanks 219121 1,501,023 7/24 Goodspeed 219-149 2,222,762 11/40 Debor et al. 219149 2,399,466 4/46 Carlson et al. 21968 2,559,227 7/51 Rieber 34012 3,007,133 10/61 Padberg 34012 FOREIGN PATENTS 742,460 12/55 Great Britain. 119,435 3/58 Russia.

OTHER REFERENCES Martin, E. A.: The Underwater Spark, An Example of Gaseous Conduction at About 10,000 Atmospheres, University of Michigan, Eng. Res. Inst., Ann Arbor, Mich. (UMN-2048-12-F), July 1956, pp. 5, 6, 11, 23, 173, and 174.

Spark-Bomb Method Promises In-Plant Explosives Forming, Space Aeronautics, February 1960, pp. 99 and 100.

Hydrospark Forming Shapes Space-Age Metals, The Tool Engineer, March 1960, pp. 81-86.

CHARLES W. LANHAM, Primary Examiner.

RICHARD M. WOOD, NEDWIN BERGER,

Examiners. 

1. AN APPARATUS FOR DEFORMING A WORKPIECE BY THE APPLICATION THERETO OF FLUID PRESSURE, COMPRISING: HOUSING MEANS DEFINING WITH THE WORKPIECE A GENERALLY CLOSED CHAMBER SUBSTANTIALLY FILLED WITH DIELECTRIC LIQUID; A PAIR OF SPACED-APART CONDUCTORS JUXTAPOSED IN SAID CHAMBER AND IMMERSED IN SAID LIQUID WHILE DEFINING BETWEEN THEM A FIRST ELECTRICAL-DISCHARGE GAP EXTENDING GENERALLY PARALLEL TO THE WORKPIECE; MEANS FORMING A SECOND ELECTRICAL-DISCHARGE GAP IMMERSED IN SAID LIQUID ALONG A SIDE OF SAID FIRST GAP REMOTE FROM SAID WORKPIECE; A FUSIBLE MEMBER BRIDGING SAID CONDUCTORS AND SPANNING SAID FIRST GAP; AND 